Generally, when it is desired to cut a pipe, it is mounted in and gripped by a chuck of a lathe and rotated while a non-rotating cutting tool is moved laterally into the rotating pipe. The cutting is accomplished in several successive turns of the pipe as the tool bit is moved gradually into the rotating pipe. The lathe requires a heavy bed which is fixed and contained in a permanent location, such as a machine shop. Additionally, the tool bit requires rigid, yet movable, holding supports. Heavy-duty power equipment is also required to operate the various components of the pipe cutting arrangement.
In the past, the lack of portable pipe cutting equipment required that all pipes be precut before transporting to an installation location. In many instances, however, the precise lengths of pipe needed for a particular installation are not known until the pipe is being installed on a section-by-section basis. When the lathe system is used, frequent trips to the machine shop are necessitated to cut the pipe into the required lengths.
Moreover, when using a fixed lathe, the pipe must be moved axially into the chuck before being clamped therein. This procedure requires sufficient space extending from the chuck to permit maneuverability of the pipe prior to insertion into the chuck.
All of the above necessities naturally resulted in cumbersome and costly procedures and equipment. One prior art cutting tool that addressed some of these concerns is disclosed in U.S. Pat. No. 3,985,051 issued to Charles K. Brown on Oct. 12, 1976, entitled “Apparatus for Cutting and Grooving a Pipe”. In the Brown device, a portable frame is used to support a cutting mechanism which is held within an arcuate member. The pipe is held in a fixed position, and the cutting mechanism moved along the arcuate member to perform an initial cut. The pipe is then manually rotated, re-fixed in position, and a second arcuate cut performed. This process continues until the complete circumference of the pipe has been cut.
While an improvement over the prior art in terms of providing a portable cutting tool, the arrangement of Brown remains relatively inefficient and unable to perform complex cuts. U.S. Pat. No. 6,981,437 issued to G. Ogawa on Jan. 3, 2006 discloses a different type of portable pipe cutting machine, where in this case the pipe is held fixed within a clamping device. A rotating, disc-like cutting blade is attached to a revolving member that moves axially about the pipe to perform the cutting motion. Again, however, the ability to create compound cuts (e.g., beveled edges and the like) is limited.
The need to form complex cuts or other designs is an important factor in site-based pipe cutting projects. Indeed, to weld two pieces of pipe together at a joint requires that the cuts on the two pieces be uniform. For example, when the pipe is cut at 90° to its longitudinal axis, bevels at a constant angle must be formed on each pipe. However, when the pipe is cut at an angle to form a mitered joint of, for example, 45°, the angle at which the bevel is cut must vary, since the mitered cut follows an elliptical path over the surface of the pipe. The manner in which this bevel varies is defined by a complicated set of trigonometric equations.
There are also devices in the prior art for cutting pipes and the like at the desired angle of cut and at different angles with selected bevels. For example, U.S. Pat. Nos. 4,143,862 and 4,216,945 both show an apparatus for automatically creating a mitered cut at a varying angle of bevel by rotating a torch and driving mechanism around the pipe. A combination of two servo motors position the cutting torch at a selected point on the surface of the pipe while an additional pair of servo motors set the angle that the torch makes with the surface of the pipe. A profile of the desired cut is then attached to the pipe. An optical sensing device is used to trace the outline of the profile. The mathematical equations defining the bevel angle are translated onto this profile in the form of a curve. This is considered to be a tedious process since each pipe needs a separate profile and, in addition, the profile must be applied to the surface of the pipe with due care.
Various other hand tools may be used to form complicated pipe cuts, but are often considered to be too slow, inaccurate and/or inefficient to utilize in any installation or production facility that requires multiple complex cuts to be performed.
Thus, a need remains in the art for a pipe cutting apparatus that is relatively simple to use, yet is able to repeatedly form complex/compound cuts in an environment where the cut requirements are changeable at a moments notice.